Tertullian, Marc 5.3.1: »Denique ad patrocinium Petri ceterorumque
apostolorum ascendisse Hierosolymam post annos quatuordecim scribit, ...«.
Irenäus, Haer 3.14. 3: Deinde post XIIII annos ascendit Hierosolymam cum
Barnaba, adsumens et Titum = Fourteen years later he went up to Jerusalem,
together with Barnabas, taking Titus along with him, too.
From this follows, that neither Tertullian nor Irenaeus read pa,lin, in Gal 2,1;
i.o.W., that Paul in their text obviously mentioned but one trip to Jerusalem;
These are interesting notes form the reconstructed Marcionite version of Galations at RadikalKritik.